Effects of Intravenous Injection and Intraperitoneal Continual Administration of Sodium Propionate on Serum Cholesterol Levels in Rats

To examine the effects of sodium propionate on serum cholesterol levels, rats were given sodium propionate intravenously and intraperitonealy. Six-week-old male Sprague-Dawley rats were kept on a cholesterol-free semisynthetic diet for 2 weeks, fasted, and given 400 microliters of saline solution intravenously supplemented with 0.01-10 mg sodium propionate. Three hours after injection of 1 mg of sodium propionate, the serum total-cholesterol level was significantly reduced (85.4 +/- 4.0 mg/dl) compared with its starting level (102 +/- 3.4 mg/dl), with the reducing effect lasting for 24 h. The intensity of the reduction increased proportionately with increased sodium propionate concentrations from 0.01 to 1 mg. Next, to evaluate the influence of continual sodium propionate administration on serum cholesterol levels, 6-week-old male rats were implanted with an osmotic pump intraperitonealy (ALZET Model 2ML2, pumping rate: 5.0 microliter/h; duration: 14 days; reservoir volume: 2,000 microliters). At day 14, serum total-cholesterol levels were reduced by continual sodium propionate administration at both 0.12 and 1.2 mg/day. The maximum percentage change in the serum total-cholesterol level was 78.5 +/- 6.7% of its starting level (111 +/- 7.1 mg/dl), observed at 1.2 mg/day at day 7. These results indicate that sodium propionate can reduce serum total-cholesterol levels in vivo.